Lens chuck



Mia-Y 1948- P. DE v. DAVAUCOURT 2,441,472-

LENS CHUCK Filed Aug. 8, 1946 Va Cour) give/ f r Patented May 11, 1948UNITED STATES PATENT OFFICE LENS CHUCK Pierre de Vitry dAvaucom-t,Bainbridge, Pa.

Application August 8, 1946, Serial No. 689,275

4 Claims. (01. 51--216) This invention relates to a lens chuck, andrelates more particularly to a chuck for holding a blocked lens blank sothat one surfaceof the blank may be operated upon, for example, by thegrinding wheel of a generating machine or by the lap of a fine grindingor polishing machine.

In the manufacture of ophthalmic lenses, it is customary to finishcompletely one side of the lens blank as a ground and polished lenssurface before commencing to work on the other side. The finished lenssurface is then cemented by means of optical pitch or other suitableadhesive to a lens block, leaving the unfinishedside of the lens blankexposed for operating upon ,it. It is, of course, necessary that thesecond lens surface be produced in predetermined and accurately alignedrelationship to the first lens surface. For this purpose, it iscustomary to block the lens with the first lens surface accuratelypositioned with respect to selected surfaces of the lens block, theseselected lens block surfaces being subsequently employed to align thelens block in a suitable chuck. In order to obtain accurate registrationwith this procedure, it is necessary to use rather elaborate blockingdevices and to exercise meticulous care in blocking the lens blank.

According to the present invention, 1 provide a chuck for holding aconventional lens block in such manner that the position of the lensblock .in the chuck is determined not with reference to selectedsurfaces of the lens block, but directly by the finished lens surface ofthe blocked lens blank. By the use of my chuck, therefore, accurateregistration of the lens blank in the usual grinding, lapping andpolishing machines may be obtained in a simple and direct manner. Whilecare is still needed in the blocking step to assure correctcentering ofthe axis of the finished lens surface with respect to the transverseaxis of the lens block, no particular attention need be paid to anyslight tilting misalignment of the finished lens surface with respect tothe longitudinal axis of the block, and hence the blocking operation isgreatly simplifled.

The principal object of the present invention is tc. provide a simple,accurate and effective chuck for a blocked lens blank by means of whicha finished lens surface may be accurately positioned with respect to thechuck irrespective of any slight tilting misalignment of the blank withrespect to the lens block.

Other objects and advantages of the present invention will be apparentfrom the following description, taken in conjunction with theaccompanying drawings, in which:

Figure 1 is a top plan view of a chuck in accordance with the presentinvention, showing mounted therein a lens block carrying a, blocked lensblank;

Figure 2 is a side elevation of the same, partly in central verticalsection along the line 2--2 of Figure 1; v

Figure 3 is a front end view thereof; and

Figure 4 is a detail view taken along the line 4-4 of Figure 2, with thelens block and lens blank omitted.

Referring more particularly to the drawings, the chuck l0 comprises ashank I l and a body l2 bifurcated by a central slot ii to form twoopposing resilient jaws ll.

The shank i 1 serves in the usual manner for securing the chuck to themachine in connection with which it is to be used, which machine may beof any desired character. My chuck is particularly useful, however, inconnection with generating machines for grinding a spherical or toricsurface, either concave or convex, on a lens blank. v The shank II isshown as cylindrical, but it will be understood by those skilled in thisart that it may be tapered, and that any other suitable means forsecuring the chuck body i2 to the intended machine may be substitutedfor the shank ll.

The jaws it are adapted to grip opposite sides of the bar-like shank l5of a conventional lens block' l6 to the face of which is cemented, bymeans of pitch or other suitable adhesive H, a lens blank iii. The lensblank I8 is shown as having a finished convex surface 19 mountedadjacent the lens block I6, and an exposed concave surface I9 which isto be operated upon while the blank is held by the chuck Ill. The faceof the lens block I6 is appropriately shaped for this type of lens. Itwill be understood by those skilled in this art that where the finished'lens surface i9 is concave, a lens block would be used having acomplementary shaped face.

will be understood also that, irrespective of the 20 are provided withpointed noses 22, best seen in Figures 1 and 4, adapted to engagedirectlythe finished surface IQ of the lens blank l8. Where a widevariety of work is to be handled, the tips of the noses 22 arepreferably convexly rounded as shown, although they may be sharplypointed,

or, alternatively, these tips may be shaped to correspond exactly to thesurface IQ of the lens as hereinafter described. The fingers 20 mayconveniently be made of thin, flat brass strip, and the body l2 may befiattended as indicated in Figure 3 to provide suitable foundations formounting the fingers 20 solidly on the body l2.

A bolt 26 having a head 21 and a threaded portion 28 is employed for thepurpose of drawing the resilient jaws ll together to grip the shank I ofthe lens block it. The bolt 28 is threaded into a threaded hole 29 inthe lower leg of the bifurcated body l2 and extends freely through analigned hole 30 in the upper leg of the body l2 in conventional manner.

As best shown in Figures 2 and 4, each of the jaws I4 is provided with arounded clamping surface 3i and an undercut portion 32. The laws l4 thuscooperate to form a dovetail slot 33 within which the shank i5 of thelens block I6 is accommodated. The front faces 34 of the laws I arepreferably concave in shape to correspond approximately to theconventional convex rear surface of the lens block [6. By reason of thisconstruction, it will be observed that, prior to tightening the bolt 26,the lens block it is free to rock in the chuck, with the shank l5assuming any desired tilted position within the range permitted by thedovetail slot 33. In inserting the blocked lens into the chuck, the lensblank is so positioned that its finished rear surface I! just engagesthe tip of each of the four locating fingers 20. The tips of the fingers20 must all be accurately located in a. common plane, and this planebears a predetermined relationship, usually a. perpendicular one, to theaxis of the chuck I0. By employing four locating fingers constructed asshown, all of the fingers may be made to engage the finished lenssurface I9 regardless of whether that surface is plano, spherical ortoric and convexor concave. The lens blank is thus accurately alignedwith the axis of the chuck Ill. The bolt 26 is then tightened, thusassuring that the lens blank is maintained in this accurately alignedrelationship to the chuck.

Where prism is to be introduced into the lens in the known manner, it isnecessary that the common plane of the tips of the locating fingers 20be appropriately inclined with respect to the axis of the chuck, ratherthan perpendicular thereto as in the more usual case where no prismeffect is desired. To obtain such tilting or inclination of the commonplane, an adjacent pair of the fingers 20 may be made the appropriateamount longer or shorter, as the case may be, than the other pair. Aswill be evident to those skilled in the art, this may be accomplishedeither by using locating fingers 20 of appropriate lengths, or byproviding shims between certain of the tips of the fingers and thefinished lens surface l9, or by making the fingers 20 longitudinallyadjustable with respect to the body [2 of the chuck by any suitablemeans (not shown) With the common plane of the tips of the locatingfingers thus appropriately disposed with reference to the finished lenssurface IS, the latter will be accurately positioned with respect to theaxis of the chuck ill to obtain the desired amount of prism in thefinished lens.

Where a considerable number of lenses having identical finished lenssurface I! are to be successively operated upon in the chuck 10 with thesame relationship of the surface ID to the axis of the chuck, I considerit preferable to shape the tips of the locating fingers 20 so as to beexactly complementary to the" surface Ii. Where my chuck is to be usedin a generating machine, this may advantageously be accomplished bygrinding the finger -tips in situ inthe generating machine by means ofthe usual cup grinding wheel or the like customarily used in connection.therewith. The generating machine is simply set to produce a surfaceidentical to the surface IS, the chuck is securely mounted in thegenerating machine without any lens block or lens, and the generatingmachine is put through its usual cycle. This will result in grinding offthe tips of the locating fingers so that they exactly correspond to thelens surface I9. By thus grinding the finger tips in situ in thegenerating machine, a high degree of accuracy may very easily beobtained. It will be noted that in this case there is short line contactbetween each locating finger tip and the lens surface I9, rather thanpoint contact as where the tips are convexly rounded as above described.The same effect of having the finger tips located in a common plane is,however, obtained.

Although, in accordance with the patent statutes, .1 have thus describedmy invention in detail in the best form in which it is known to me, itwill be evident to those skilled in the art that changes andmodifications may be made without departing from the spirit of myinvention. I desire to be limited, therefore, only by the scope of theappended claims.

I claim:

1. A chuck for holding a blocked lens, comprising in combination, abifurcated chuck body each leg of which constitutes a resilient chuckJaw, means for compressing said legs together to cause said jaws toclamp opposite sides of the bar-like shank of a lens block, said Jawsbeing provided with rounded shank-engaging surfaces and with undercutportions forming a dovetail slot, whereby said shank may be rocked insaid slot into a desired position prior to clamping thereof, and fourlocating fingers mounted two on each leg of said chuck body indiametrically opposed pairs and having tips adapted to engage the rearsurface of a lens blank cemented to said lens block.

2. 'A chuck for holding a blocked lens adhesively secured to a lensblock preparatory to abrading a surface of the lens opposite the surfacewhich is adhered to the block comprising, in combination, a chuck bodyincluding a pair of movable laws, shank engaging surfaces on said jawsengageable with the shank of a lens block disposed between the said jawsto clamp said lens block into a desired position within a substantialrocking range, means for compressing said jaws together to clamp saidshank, and locating fingers rigidly mounted on said chuck body andhaving tips adapted to engage the surface of a lens blank cemented tosaid lens block holder opposite to the surface to be abraded.

3. A chuck for holding a blocked lens adhesively secured to a lens blockpreparatory to abrading a, surface of the lens opposite the surfacewhich is adhered to the block comprising, in combination, a chuck bodyincluding a clamp for holding the shank of a lens block, shank engagingsurfaces on said clamp constructed and arranged to clamp said shank intoa desired position within a substantial rocking range, and aligningmeans terminating in a substantially common plane carried by and rigidlytired to said chuck body adapted to engage a surface or the lens blankcemented to said lens block opposite to the surface to be abraded toalign said blank with respect to said chuck irrespective oi any slighttilting misalignment of the lens blank with respect to the lens block.

4. A chuck for holding a blocked lens adhesively secured to a lens blockpreparatory to abrading a surface or the lens opposite the surface whichis adhered to the block comprising, in combination, a bifurcated chuckbody. each leg of which constitutes a resilient chuck Jaw, means forcompressing said legs together to cause said jaws to clamp oppositesides of the shank of a lens block, shank engaging surfaces on said jawsso constructed and arranged as to engage said shank in a desiredposition within a substantial rockins range, and four locating fingersrigidly mountgo ed on said chuck in diametrically opposed pairs andhaving tips terminating in a common plane adapted to engage the surfaceof a Iens blank cemented to said lens block holder opposite the surfaceto be abraded to align said blank with 5 respect to said chuckirrespective of any slight tilting misalignment of the lens blank withrespect to the lens block.

PIERRE DI VITRY DAVAUCOURT.

10 REFERENCES CITED The following references are oi record in the iileof this patent:

, UNITED STATES PATENTS 15 Number Name Date 1,202,013 Ainsley Oct. 24,1916 1,494,333 Bausch May 20, 1924 1,727,889 McCabe Sept. 10, 19292,253,954 Goddu Aug. 26, 1941 2,381,573 Canning Aug. 7, 1945 2,398,790

Holman Apr. 23, 1946

